This project is a joint collaboration between researchers at Columbia, Johns Hopkins, and the University of Rochester to determine(i) the extent to which viral burden and markers of macrophage activation (tumor necrosis factor-alpha [TNFa], soluble TNF-r2, beta-2-mircoglobulin [B2M]) are related to severity of functional deficit in people with HIV; and (ii) which aspects of function (as derived from self-report, clinician assessment, and daily time use) are most sensitive to variation in viral load and markers of macrophage activation. Because functional deficit can have many sources, detailed psychiatric, neurologic, and neuropsychological assessments will be obtained. Also, because functional status includes varying kinds of abilities (which may be affected by different components of the disease process), a number of functional assessments will be conducted including ratings of respondents' observed ability to manage HIV-specific care tasks (e.g., ability to take medications properly) and related survival skills. Seventy-five men and women seropositive for HIV will be enrolled in this research. For this project, subjects will be continually enrolled in the study to replace those who die or are lost to follow-up. Subjects will be seen at six-month intervals over five years.